2026/07/27 by Kosei Nakagawa, Yoshiko Kanada-En'yo
#nucl-th
We investigate the cluster structure of α+2n+2n in 8He(02+) and compare it with those of 2α+2n in 10Be(02+) and 3α in 12C(02+) to understand the emergence mechanism of the 3-body cluster gas states. We apply an extended cluster model combined with cluster breaking components in a microscopic framework using effective nuclear forces based on nucleon degrees of freedom including the antisymmetrization between nucleons. In detailed analysis of the 3-body cluster structures of excited 0+ states, it is shown that 8He(02+) exhibits 3-body cluster gas feature of α+2n+2n similar to 12C but contains significant mixing of a 2-body-like (α+2n)+2n component. We discuss cluster structures of 8He(02+) and 12C(02+) from the point of view of inter-cluster energies of 2n - 2n and α-2n in comparison with the α- α energies and find that the origin for the 2-body-like (α+2n)+2n mixing is the unbalance of the α-2n and 2n - 2n energies, in which Pauli effects play an essential role through the kinetic energy loss and internal potential energy loss of clusters. We clarify the emergence mechanism of the 3-body cluster gas state in excited 0+ states of 8He and 12C systems. The balance of inter-cluster interactions is essential for the appearance of 3-body cluster gas states. Microscopic effects, i.e., the Pauli effects of nucleons between clusters play a crucial role in cluster structures of excited 0+ states.